If you have to work those hours then you are being "used". Unless you have major equity (5%+) Your are just being a tool for the founders to get rich. That's it. Your equity is not worth it, plus you will never get those months/years back.

Find another job, where you can have normal hours, and can have time for friends, fun, and hobbies, and creating an app, or open source project/whatever rocks your boat.

Life is too short to spend every minute of it making somebody else rich.